1. Field
Example embodiments relate to an unlatching tool and in particular to an unlatching tool for unlatching a control rod blade of a nuclear reactor. Example embodiments also relate to a method of unlatching a control rod blade of a nuclear reactor.
2. Description of the Related Art
FIG. 1 illustrates a simplified diagram of a typical boiling water reactor building 10. As shown in FIG. 1, a typical nuclear reactor building 10 houses, among other things, a crane 15, which may be used to move relatively heavy equipment in the reactor building 10. The reactor building 10 also houses a nuclear reactor pressure vessel 20 which includes a dome-shaped top head 25, a plurality of fuel assemblies 35, and a plurality of control rods 45. A top guide 30 is arranged over the fuel assemblies 35 and resembles a grid having a plurality of rectangular cells. At the bottom of the fuel assemblies 35 is a fuel support casting 40 and below the fuel support casting 40 are guide tubes 50 housing the control rod 45.
FIG. 2 illustrates a conventional control rod 45. As shown in FIG. 2, the typical control rod blade 10 includes four wings 45a, 45b, 45c, and 45d arranged in a cruciform shape. Each of the wings 45a, 45b, 45c, and 45d include a neutron absorbing material.
In a typical reactor assembly, the control rod 45 are arranged below the fuel assemblies 35 and are latched to control rod drives that enter the reactor pressure vessel through a housing welded to the bottom head of the reactor pressure vessel. The drives are basically hydraulic cylinders, operated by hydraulic control units. In operation, a control rod drive may move a control rod 45 upwards and between four fuel assemblies 35 in order to moderate/control the activity of the nuclear reactor.
FIG. 2 illustrates a detailed section of a bottom 46 of a control rod 45. The bottom 46 of the control rod 45 includes a velocity limiter 48, a coupling socket 47, and a D-handle 49. For maintenance purposes it may be desirable to unlatch the control rod 45 from their respective control rod drives. However, in order to unlatch the control rods 45 from the control rod drives, the control rod D-handle 49, located at the bottom of the control rod 45, must be accessed.